Time was, the solar system was raining rocks. You only need to look at the cratered face of airless bodies like Mercury and the moon to get a sense of the cosmic crossfire that took place back when the local worlds were just forming and much of the debris that helped make them up was still flying free. Even now, planets and moons occasionally swap rubble, with odd bits of, say Mars, blasted into space by a long-ago meteor spiraling slowly in to get snagged by Earth.

This kind of planetary tissue exchange long ago gave rise to the concept of panspermia — the idea that life on Earth may not have originated here at all, but rather was imported in the form of organic building blocks or even microorganisms from far away. Earth, in turn, may have similarly seeded other worlds. The catch is that the solar system is a limited place, with Earth the only place we know of that’s currently capable of supporting wandering biology.

Things get a lot more interesting if you expand the pool of candidate worlds to include those in other solar systems. This idea, called lithopanspermia, has always seemed like a nifty possibility, but not one worth much thought. The physics of interstellar transfer are so complex that it would, for practical purposes, be impossible for any debris to make such a journey. Or that was the belief. But a new paper published in the journal Astrobiology gives new energy to the lithospermia idea — concluding that interstellar transfer of life might be a whole lot more possible than anyone expected.

For astrophysicists, the easiest part of both panspermia and lithopanspermia has paradoxically been the biology itself. The universe is fairly awash in water, hydrocarbons and even amino acids — and all of them can be carried aboard free-flying space rubble. In 2011, geologists announced that a meteorite that landed on Earth in 2000 not only contained amino acids and other prebiotic materials, but that all of them existed in different stages of complexity — meaning that the meteor had actually been cooking them up en route, probably with the help of traces of on-board water and heat released by radioactive material.

But if organic cargo can survive — and even thrive — on such a long journey, there’s still the matter of how you ship it from sender to receiver, and here’s where lithopanspermia ran into trouble. Old models of interstellar transfer relied on the idea of rubble being flung out of a solar system by gravitational encounters with large bodies like Jupiter, meaning that they’d be traveling at speeds of about 8 km per second — or nearly 18,000 mph. That’s way too fast for the rocks ever to be captured by the gravity of another star system, even if they did reach one. “It is very unlikely that even a single meteorite originating on a terrestrial planet in our solar system has fallen onto a terrestrial planet in another solar system, over the entire period of our solar system’s existence,” wrote astrophysicist H. Jay Melosh of the University of Arizona in a 2003 paper that attempted to put the lithopanspermia idea to rest once and for all. If our rocks can’t get out, other rocks have no greater chance of getting in.

That, however, is only if you stick with the old model for how the debris was set free in the first place. A team of researchers from Princeton University, the University of Arizona and Centro de Astrobiologia in Spain took a different approach, developing computer models of a slow-boat transit method known as weak transfer. Under this process, rubble spirals slowly outward through a solar system until it reaches a spot so far from its parent sun that it requires only a slight perturbation to nudge it into interstellar space. “At this point,” says Princeton astrophysicist Edward Belbruno, one of the authors of the paper, “you’re escaping so slowly that randomness and chaos theory is involved in getting you out.”

The problem is that low speed can also mean slow transit time to the next solar system, with a trip lasting 1.5 billion years or more, longer than even the toughest organic material could survive. About 4.5 billion years ago, however, when the sun was just being born, it was part of a tight grouping of nascent stars known as the local cluster that was comparatively densely packed — and that could have cut transit times dramatically.

“After about 100 to 200 million years, the stars scattered, and the transfer likelihood went dramatically down,” says Belbruno. “But you do have a window.” Encouragingly, analyses of terrestrial rocks reveal that Earthly organics may indeed have formed in the solar system’s comparative babyhood, directly within the departure window.

On its face, the number of rocks that would reach another solar system seems small — 5 to 12 out of every 10,000. But since trillions of rocks per year make the low-speed escape, that means a whopping one billion in that same year might be captured by neighboring worlds — and we could be on the receiving end of similar numbers from elsewhere. It may still be unlikely that anyone alive today will ever meet an alien— but the odds just went up a little that we all could be the aliens.

I remember this crackpot theory coming out when NASA was desperately trying to say they found like on Mars. They claimed an impact hit mars and sent debris to earth. Let's put a little logic into this shall we. Any impact big enough to drive debris out into orbit and out of the gravitational field of mars would have sent the debris up in a semi-molten state, the rocks would have spend millenia in space before getting to earth being bombarded by intense heat, cold, and radiation. The debris would then fry hitting the atmosphere. And to top it off the rock, has been sitting for years, perhaps millions, and them some dumb science shmuck says there is earthlike creatures in the rock.... Of course it does, it wasn't picked up the instant it landed!!!!

The million images sent to earth by various telescopes show that the various solar systems and galaxies are spinning like cyclones. Under the centripetal force dispersals millions of meteors are escaping at very slow tangential velocities into inter stellar space. The speeds range from supersonic to very sluggish. At such slow speeds neither organic vapor nor heat is severely lost from the travelling object especially at very low temperatures. ThatThat at least explains Why icy comets can remain frozen and supportive of molecular life preservation by the time they arrive other solar systems or galaxies. Life in such scenario is formed at random on those planets whose atmospheres are conducive to metabolic synthesis of organicf life.

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I believe in the God who said "Let There Be Light" - and in so doing created the "Big Bang" that you love to believe in - and from that act came everything else that has ever been created. When you demonstrate, conclusively that the Universe stemmed from some other cause I will listen to you. Until then, I'll believe in the Truth as presented in the World's most important book - The Holy Bible.

Life on earth was actually already on its way because the solar system had the necessary elements of life that were inherited to the sun being a second generation star from an exploding supernova. These heavy elements were elaborated at the core of the massive star that spread through space in the resulting debris that were

driven away in the cloud that eventually formed our solar system with the sun

and our earth. These elements exist today in our own bodies: carbon, oxygen,

This article doesn't make a lot of sense if we take into consideration outside earth's or any other liveable planet's conditions. No biological object will escape radiation and extremes of tempreratures.. In other words, you get off the pond, you die..

Inventing absurd definitions of atheists, and concocting critiques of the Origin with nonsense about what caused it ... it's a sad reflection of the need to find a religious angle; the article is about new research on the physical drivers in the Universe.

But if it is going to get hijacked by the same old anti-reality groups, then listen up - it lays out very simply, and put very eloquently, by the conclusion of Stephen Hawking - God didn't create the Universe because there was no time to create God before it.

And what, pray tell, is your explanation for the cause of the "Big Bang?" There isn't one "atheist" alive who hasn't thought about where the Universe came from - or in these days, "what caused the Big Bang." That's the reason they claim to be Atheists - because it's so plainly obvious that the God of the Bible created it all when He said "Let There Be Light," the people who call themselves "Atheists" only do so because they desparately want not to believe that they have souls which will live on beyond their bodies - and may be answerable for their refusal to accept the tenets of Christianity. As you said, a lot of people don't spend any time thinking about these thing. In most cases, that's because when they start to ponder them, they get frightened so they use every mental trick they can find (including the belief that "it all just happened") to convince themselves that they don't have to worry about it.

The more science advances the more desperate the religious die hards become. If they cannot accept that millions of chance meetings over billions of years produces more sophisticated life forms, they should have a look at a Mexican walking fish and think again.

I'd love to see your research that a man named Moses existed or that Jews were kept as slaves by the Egyptians and escaped into the desert ever took place. You can quote one source and one source only, the Bible.

Let's face it, either there is a dynamic that wipes out life, a glass ceiling that life can't escape, or there is a tremendous number of species scattered across our galaxy. I could tell you numerous possible scenarios where life inevitably can't reach intra-solar system travel (for instance, a life ending event that happens every once in a while throughout the galaxy).

My opinion is that we are likely quarantined either practically, or through some system of enforcement, and there are many many intelligent species out there.

i do believe that this article is on the right path. we humans are only a small part of a very big thing, most of which we don't understand yet. a friend was told she was an ET Master but she said she doesn't know what to do with that information. all in all, although it's shocking to think about, we humans may be in the mix of a radical species recipe.

1978 - 'There are those who believe that life here began out there' Battlestar Galactica - I'm afraid, people have absorbed too much TV and Movies. Carl Sagan used hollywood and hypnotic Vangelis music. After so many years people really now believe that E.T. is real. I also grew up playing with starwars figures, but that doesn't mean, I think they actually exist. If you can't come up with an explanation for spontaneous generation on this planet... than how did life come from nothing on another? still takes a huge amount of faith as someone else said.

At its most fundamental level, life is a molecular process of self-replication - that's it. Before we get eyes or ears or biological complexity (which occurs through evolution), we just need molecules to combine and make copies of themselves; everything else is cheddar. There are some great videos about this, and why H2O acts as a good solution for this basic chemical process to occur; it has to do with the charge properties of atoms - really neat stuff.

Why are scientists always looking for "how man was created?" It is so simple....God is our creator; why is that such a problem? I challenge all skeptics to explore the bible and prove it wrong. You can't!

"Time was, the universe was raining rocks". Who writes these things? Even worse, how does it get past an editor? Time is a reputable publication, but these sorts of mistakes make me question the writers, editors, and the validity of their claims.

Funny how people will believe this nonsense amp; yet not believe that God is the Creator of all things. I would like to see all you skeptics out there try something new.....study the Bible and PROVE it wrong. You can't do it!

ATHEISM: The belief that there was nothing, and nothing happened to nothing and then nothing magically exploded for no reason, creating everything, and then a bunch of everything magically rearranged itself for no reason whatsoever into self-replicating bits which then turned into dinosaurs. Makes perfect sense, right?

If life was exchanged between the member star systems of our " local cluster", then in which solar system (exact name) would have life initially started so that it could then be shared with the others including the Sol system?

And wide-binary core collapse may be the 'weak transfer' mechanism for evaporating trillions of planetesimals (comets) from stellar equivalents of our own 'outer Oort cloud'. Weak transfer of energy and angular momentum from wide-binary stellar pairs to planetesimals would cause them to gradually exceed the stellar Hill spheres, enabling galactic perturbation to detach planetesimals at the required slow speeds for subsequent capture by other stellar systems .

Our own solar system may be a model for this type of core-collapse evaporation if Proxima (Centauri) is a companion star to our Sun in a temporary, unbound hyperbolic orbit around the passing binary star ,Alpha Centauri AB.

Does anyone else reading this find it as absolutely absurd as me? It sure takes a lot of faith to believe this is even a possibility as opposed to a Creator, which takes faith but explains everything a whole lot more easily. As a student of science, I can't get beyond the law which states that everything always goes from order to disorder.